The present invention relates to a technology for a method of manufacturing a semiconductor device. In particular, it relates to a technology which is effective when applied to the manufacture of a semiconductor device including a process of depositing thin films over a semiconductor wafer with use of a sputtering technique. Further, the present invention relates to a sputtering apparatus and, in particular, it relates to a technology which is effective when applied to the puttering apparatus having a collimator.
Among manufacturing processes of a semiconductor device, the sputtering apparatus is widely used in a process of depositing a conductive thin film for an integrated circuit over a semiconductor wafer (hereafter, also simply called a “wafer”).
As one of the thin film formation techniques using this kind of sputtering apparatus, there is known a collimate sputtering technique in which a disc-like member with numbers of through holes called a collimator is arranged between a wafer and a target provided in a sputtering chamber.
The collimate sputtering technique is the one in which sputtered particles entering a main surface of the wafer obliquely from the target is reduced by the collimator and sputtered particles having many vertical components are allowed to enter the wafer so that coverage, for example, at the bottom portion of a connection hole with a high aspect ratio can be improved.
Since wafers are becoming larger in diameter these years, in a thin-film formation process using a sputtering apparatus, uniformity of the film thickness distribution between a central part and a peripheral part of the wafer has been deteriorated significantly.
As one of the measures to cope with the situation, Patent Document 1 (International Publication WO2004/047160) discloses a technique in which, among numbers of through holes provided in the collimator, an aspect ratio (depth of a hole/diameter) of through holes located on a central part side of the collimator is made higher than that of through holes located on a peripheral part side of the collimator.
According to the technique disclosed in Patent Document 1, the amount of sputtered particles passing through the through holes of the collimator becomes larger on the peripheral part side than on the central part side of the collimator. Therefore, it can be expected that relative shortage of the film thickness in the peripheral part of the wafer is compensated and uniformity of the film thickness distribution in a wafer plane is improved.